So much great help. I appreciate your giving me your time.
I do have the paper manual that came with the H2, and I can track with you as you cite page numbers.
Trying to respond to everything in order, but probably failing:
I noticed my friend (in the Zoom interview) is using a desk mic and a wired one-ear headphone. That’s what I plan to do from now on.
Like you, I mistrust wireless ear buds, for something this important and possibly live.
I always use “Front” and “Mono” (that seems to be what people want for speech).
It’s not hard to find the USB modes. As soon as I plug it in (whether using the USB cable or the Plextone + Aux), I get a choice of “Storage” or “Audio I/F”. so I select the Audio I/F.
Next it says “Frequency 44.1 kHz” or “Connect.” I click “Connect.”
Then I click the red button once, so the red light is flashing. I don’t need it to record to the SD card, so once is enough.
Here’s the weird thing. If I’m using the USB cable, wait a second, then open Audacity, the H2 is there as one of the mic choices. So I click it and click the red Record button–and the cursor does not move. It looks like the attached screenshot.

I can see the volume lines moving on the H2. But Audacity apparently doesn’t hear anything. Likewise when I check it on Zoom Settings > Audio, it plays back nothing.
In both cases (Audacity and Zoom), I get good results when I use the Plextone connector with the H2.
BTW I opened the Control Panel and then went to Manage Audio Devices, and didn’t see a way there to monitor audio. I could set things, like mic gain, but not record/play and monitor something.
Love the recording in a cave. That was genius.
I had never set AGC / Comp. I see it is set to “Off” at present. What setting do you recommend?
I am looking for Dell Audio, but can’t turn anything up:

Gradually working our way through!
I guess what we’ve settled is that the H2 should be capable of handling Zoom interviews well. I’ll use a single-ear wired earbud.
And the computer doesn’t seem to like the H2 USB connection, though it knows it’s there.